Hot-melt silicone pressure sensitive adhesive with siloxylated polyether waxes as additives

ABSTRACT

The instant invention pertains to a hot-melt pressure sensitive adhesive composition wherein the composition is comprised of a silicone pressure sensitive adhesive selected from the group consisting of a mixture of (i) a silicone resin and (ii) a silicone fluid and a condensed product of (i) and (ii); the silicone pressure sensitive adhesive exhibiting tackiness and adhesiveness; the silicone pressure sensitive adhesive being blended with (iii) from about 1 to 20 weight percent, based on the total weight of (i) and (ii), of a siloxylated polyether wax. The instant invention also encompasses method of using the composition, methods of making hot-melt silicone pressure sensitive adhesive-coated substrates, and devices made using the composition.

This is a divisional of application Ser. No. 08/181,508 filed on Jan.14, 1994, now U.S. Pat. No. 5,482,988.

BACKGROUND OF THE INVENTION

A pressure sensitive adhesive (PSA), generally, is a material whichadheres to a surface with slight pressure and releases from the surfacewith negligible transfer of the material to the surface. Siliconepressure sensitive adhesives that are known in the art are typicallysolvent based adhesives; the solvents are employed primarily to reducethe silicone pressure sensitive adhesive's viscosity to a viscositywhich is easily coated onto the substrate of choice, and the solventsare removed after coating.

Hot-melt pressure sensitive adhesives are those adhesives, which uponheating, melt to viscosities suitable for coating, but when cooled aregenerally in a flowless state. The advantages of hot-melt PSA's relativeto solvent-based PSA's are known and include safety, environmental andapplication advantages. In addition, hot-melt PSA's have the advantageof not containing solvents which sometimes interfere with the additionof other ingredients to the PSA. Silicone pressure sensitive adhesiveshave been found to be preferred over other types of PSA's in manyapplications, especially in the medical area. Pressure sensitiveadhesives have long been used to bind bandages, sensory monitors, andthe like to a person's skin. In addition, silicone pressure sensitiveadhesives have found use in transdermal drug delivery applications whichinvolve the adherence of a drug-containing patch to a patient's skin.

U.S. Pat. No. 4,865,920 discloses a hot-melt PSA comprised of (i) asilicone resin, (ii) a silicone fluid and (iii) an ester having theformula R'--C(O)OR" wherein R' is a monovalent hydrocarbon radicalhaving from 2 to 32 carbon atoms and R" is a monovalent hydrocarbonradical having from 1 to 14 carbon atoms.

Other additives, besides the esters, have recently been developed whichare capable of reducing the dynamic viscosity of the PSA while alsoimparting other beneficial properties into the PSA. For example, U.S.Pat. No. 5,162,410 discloses a hot-melt PSA comprised of (i) a siliconeresin, (ii) a silicone fluid and (iii) at least one phenyl-containingpolysiloxane fluid having a viscosity at 25° C. of from about 5 to60,000 centistoke. The compositions of U.S. Pat. No. 5,162,410 aredisclosed as being more compatible with certain drugs and other organicmaterials than are the hot-melt PSA's of U.S. Pat. No. 4,865,920.

EP Application No. 0 443 759 discloses a hot-melt PSA comprised of (i) asilicone resin, (ii) a silicone fluid and (iii) a non-flammablehydrocarbon having weight average molecular weight of from about 300 to1500. The compositions of EP Patent Application No. 0 443 759 aredisclosed as being more compatible with certain drugs and other organicmaterials than are the hot-melt PSA's of U.S. Pat. No. 4,865,920.

These hot-melt compositions have been found to be inadequate for thedelivery of hydrophilic drugs from transdermal drug delivery systems.There are several advantages to having a hot-melt composition that ishydrophilic. One advantage is that higher dosages of hydrophilic drugscan be employed without destroying the pressure sensitive adhesive.Another advantage is that the amount of drug released can be increasedor controlled. Finally, the conditions under which a patch can be wornare greatly improved.

It is an object of this invention to provide a hot-melt siliconepressure sensitive adhesive composition that has improved hydrophiliccharacteristics while maintaining the pressure sensitive adhesiveproperties of shear, adhesion, and release.

SUMMARY OF THE INVENTION

The instant invention pertains to hot-melt pressure sensitive adhesivecompositions which possess the benefits of being hot-melt adhesives andbeing formed of materials which are highly acceptable in topicalapplications. The hot-melt silicone pressure sensitive adhesivecompositions of the instant invention have improved hydrophiliccharacteristics while retaining adhesion, shear and release.

The hot-melt silicone pressure sensitive adhesives of the instantinvention are comprised of a silicone pressure sensitive adhesiveselected from the group consisting of a mixture of (i) a silicone resinand (ii) a silicone fluid and a condensed product of (i) and (ii); thesilicone pressure sensitive adhesive exhibiting tackiness andadhesiveness; the silicone pressure sensitive adhesive being blendedwith (iii) from about 1 to 20 weight percent, based on the total weightof (i) and (ii), of a siloxylated polyether wax. The instant inventionalso encompasses method of using the composition, methods of makinghot-melt silicone pressure sensitive adhesive-coated substrates, anddevices made using the composition.

THE INVENTION

The hot-melt silicone pressure sensitive adhesive of the instantinvention is comprised of a silicone pressure sensitive adhesiveselected from the group consisting of a mixture of (i) a silicone resinand (ii) a silicone fluid and a condensed product of (i) and (ii); thesilicone pressure sensitive adhesive exhibiting tackiness andadhesiveness; the silicone pressure sensitive adhesive being blendedwith (iii) from about 1 to 20 weight percent, based on the total weightof (i) and (ii), of a siloxylated polyether wax.

Component (i) of the instant invention may be further described as beinga soluble, hydroxyl-functional organopolysiloxane resin comprising R₃SiO_(1/2) siloxane units and SiO_(4/2), wherein R is selected from amonovalent radical selected from the group consisting of hydrocarbon andhalogenated hydrocarbon radicals having 1 to 20 carbon atoms. By theterm soluble it is meant that the organopolysiloxane can be dissolvedsubstantially completely, in either a hydrocarbon liquid such asbenzene, toluene, xylene, heptane and the like or in a silicone liquidsuch as cyclic or linear polydiorganosiloxanes. Preferably the resin issoluble in the silicone fluid (ii).

In the formula for resin (i), R denotes a monovalent radical selectedfrom the group consisting of hydrocarbon and halogenated hydrocarbonradicals, preferably having less than 20 carbon atoms, and mostpreferably having from 1 to 10 carbon atoms. Examples of suitable Rradicals include alkyl radicals, such as methyl, ethyl, propyl, pentyl,octyl, undecyl, octadecyl and others; cycloaliphatic radicals, such ascyclohexyl; aryl radicals such as phenyl, tolyl, xylyl, benzyl,alpha-methyl styryl, 2-phenylethyl and others; alkenyl radicals such asvinyl; and chlorinated hydrocarbon radicals such as 3-chloropropyldichlorophenyl and others.

To enhance the solubility of component (i) in component (ii) it isdesirable to select the predominant organic radicals of the former tomatch the predominant organic radicals of the latter. Preferably, atleast one-third, and more preferably substantially all R radical in theformula for component (i) are methyl radicals. Examples of preferred R₃SiO_(1/2) siloxane units include Me₃ SiO_(1/2), PhMe₂ SiO_(1/2) and Ph₂MeSiO_(1/2) where Me denotes methyl and Ph denotes phenyl.

It is preferred that the ratio of R₃ SiO_(1/2) siloxane units toSiO_(4/2) units has a molar ratio of 0.5 to 1.2 respectively. It isfurther preferred that the mole ratio of the total R₃ SiO_(1/2) siloxaneunits to SiO_(4/2) units be between 0.6 and 0.8

Component (i) can be prepared by well known methods. It is preferablyprepared by the silica hyrosol capping process of U.S. Pat. No.2,676,182 to Daudt et al.; as modified by U.S. Pat. No. 3,627,851 toBrady; and U.S. Pat. No. 3,772,247 to Flannigan; each patent beingincorporated herein by reference to teach how to prepare solubleorganopolysiloxanes which are useful in the instant invention. Theresulting resin can be used in the instant invention without furthermodification or it can be capped with trialkylsilyl groups to reduce thesilanol content. This can be accomplished by well known methods, such asreacting the resin with a compound such as trimethylchlorosilane orhexamethyldisilazane.

Component (ii) of the instant invention is a silicone fluid, preferablya hydroxyl-terminated diorganopolysiloxane polymer. The repeat units of(ii) are R₂ SiO_(2/2) siloxy units wherein R is independently selectedfrom the same hydrocarbon and halogenated radicals defined above forcomponent (i). This component can be comprised of a single polymer orcopolymer or it can be a mixture of two or more such polymers. For thepurposes of the present invention, each polydiorganosiloxane polymershould have a viscosity at 25° C. of about 100 to 500,000 centipoise(cP), preferably 500 to 50,000 and most preferably 1,000 to 20,000 cP.It is preferred that at least 50%, and preferably at least 85%, of theorganic radicals along the chain component (ii) are methyl radicals,which can be distributed in any manner in the diorganopolysiloxane.Further, component (ii) can comprise up to about 10 mole percent ofsiloxane branching sites provided it meets the above viscosityrequirements.

The silicone resin is employed in amount from about 40 to 70 parts byweight in the silicone pressure sensitive adhesive, and the siliconefluid is employed from about 30 to about 60 parts by weight, wherein thetotal parts of the silicone resin and the silicone fluid are 100 parts.It is usually preferred that the silicone resin be employed from about50 to 60 parts by weight, and correspondingly, the silicone fluid beemployed from about 40 to 50 parts by weight, wherein the total parts byweight equals 100.

Additionally, the silicone pressure sensitive adhesive which is mixedwith the siloxylated polyether wax may be selected from various knownsilicone pressure sensitive adhesives which may or may not be condensedproducts of (i) and (ii). The hot-melt silicone pressure sensitiveadhesive of the instant invention do not employ solvents that are foundin traditional PSA's.

One suitable class of pressure sensitive adhesives to be employed in thehot-melt composition of the instant invention consists of a mixture of atrimethylsilyl-endblocked polysilicate resin such as a silicone resinconsisting of a benzene-soluble resinous copolymer containingsilicon-bonded hydroxyl radicals and consisting essentially oftriorganosiloxy units of the formula R¹ ₃ SiO_(1/2) and tetrafunctionalsiloxy units of the formula SiO_(4/2) in a ratio of about 0.6 to 0.9triorganosiloxy units for each tetrafunctional siloxy unit present inthe copolymer, wherein R¹ is a monovalent organic radical independentlyselected from the group consisting of hydrocarbon radicals of from 1 to6 carbon atoms, and (ii) a silanol-endcapped polydiorganosiloxane fluidsuch as a polydimethylsiloxane fluid. U.S. Pat. No. 2,736,721 to Dexter,et al. and U.S. Pat. No. 2,814,601 to Currie, et al. are herebyincorporated by reference to teach of such or similar pressure sensitiveadhesive compositions.

Another class of suitable pressure sensitive adhesives to use accordingto the invention is that or those similar to the pressure sensitiveadhesives in U.S. Pat. No. 2,857,356 to Goodwin, Jr., which is herebyincorporated by reference. U.S. Pat. No. 2,857,356 discloses a siliconepressure sensitive adhesive which consists of a mixture of ingredientscomprising (i) a cohydrolysis product of a trialkyl hydrolyzable silaneand alkyl silicate, wherein the cohydrolysis product contains aplurality of silicon-bonded hydroxy groups, and (ii) a linear, highviscosity organopolysiloxane fluid containing silicon-bonded hydroxygroups.

The silicone resin (i) and the silicone fluid (ii) may optionally becondensed together according to a procedure such as described inCanadian Patent 711,756 to Pail, which patent is hereby incorporated byreference. In such a condensation reaction, the silicone resin (i) andsilicone fluid (ii) are mixed together in the presence of a catalyticamount of a silanol condensation catalyst, and then the silicone resin(i) and the silicone fluid (ii) are condensed, for example, by heatingunder reflux conditions for 1 to 20 hours. Examples of silanolcondensation catalyst are primary, secondary and tertiary amines,carboxylic acids of these amines and quaternary ammonium salts.

Another class of suitable pressure sensitive adhesives to use with thesiloxylated polyether waxes, according to this invention, are thosecompositions described in U.S. Pat. No. 4,591,622 and No. 4,584,355 toBlizzard et al., No. 4,585,836 to Homan et al., and No. 4,655,767 toWoodard et al, hereby incorporated by reference. Generally, thesepressure sensitive adhesives consist of a blend of (i) a silicone resinand (ii) a silicone fluid which are chemically treated to reduce thesilicon-bonded hydroxyl content of the blend. These adhesives mayoptionally be condensed, as described previously, prior to the chemicaltreatment.

The silicone pressure sensitive adhesives useful in the instantinvention should not be confused with silicone rubbers which are notuseful. The silicone pressure sensitive adhesives are usually fillerlessor contain low amounts, less than 5%, of fillers. On the other hand,silicone rubbers typically contain about 15 to 35% filler. Fillers aregenerally not required in high quantities in silicone pressure sensitiveadhesives, because high quantities often cause the silicone pressuresensitive adhesives to lose tack and adhesiveness and to increase indynamic viscosity, making it more difficult to apply a coating of thesilicone pressure sensitive adhesive.

Component (iii) of the instant invention is a siloxylated polyether wax.Generally, any silicone polymer that contains a alkyl wax (≧C₆)functionality and polyethylene oxide functionality will be useful in theinstant invention. The siloxylated polyether waxes (iii) of the instantinvention may be exemplified by silicone polymers having the generalformula ##STR1## wherein each R² is independently selected from thegroup consisting of an alkyl radical having 1 to 4 carbon atoms, aphenyl radical and a hydroxyl radical; R³ is an alkyl radical having 6or more carbon atoms; A is a polyethylene oxide group selected from thegroup consisting of --R₄ O(CH₂ CH₂ O)_(a) R₅ and --R₄ O(CH₂ CH₂ O)_(a)(CH₂ (CH₃)CHO)_(b) R₅ where R⁴ is an alkylene radical having from 1 to 6carbon atoms; R⁵ is selected from the group consisting of --H and--COCH₃ ; a has a value of at least 1, and b has a value of at least 1,x has a value of greater than 0; y has a value of greater than 0; and zhas a value of 1 to 100.

In the formulas for the siloxylated polyether waxes (iii), R² isselected from the group consisting of an alkyl radical having 1 to 4carbon atoms, a phenyl radical and a hydroxyl radical. Examples ofsuitable R² radicals include, but are not limited to, methyl, ethyl,phenyl and hydroxyl. Preferably at least 90 mole percent of the R²radicals are methyl and more preferably all of the R² radicals aremethyl.

R³ in the preceding siloxylated polyether wax formulas is selected froman alkyl radicals having 6 or more carbon atoms. Examples of R³ include,but are not limited to, hexyl, octyl, decyl, dodecyl, tetradecyl,hexadecyl, octadecyl, eicosyl, tetracosyl, and triacontyl.

"A" in the preceding siloxylated polyether wax formulas is apolyethylene oxide group selected from the group consisting of --R₄O(CH₂ CH₂ O)_(a) R⁵ and --R₄ O(CH₂ CH₂ O)_(a) (CH₂ (CH₃)CHO)_(b) R⁵where R⁴ is an alkylene radical having from 1 to 6 carbon atoms; R⁵ isselected from the group consisting of --H and --COCH₃ ; a has a value ofat least 1, preferably at least 20; and b has a value of at least 1. Itis generally recognized by one skilled in the art that the presence ofpolypropylene oxide groups can be detrimental to the hydrophilicitytherefore it is further preferred that when "A" is the group R₄ O(CH₂CH₂ O)_(a) (CH₂ (CH₃)CHO)_(b) R⁵ that b has a value of 1 to 20 and thata+b≧50. One skilled in the art will be able to readily determine theamount of polypropylene oxide that can be present without losing thehydrophilic characteristics of the wax. R⁴ may be exemplified by, butnot limited to, methylene, ethylene, propylene, butylene and others.

In the preceding siloxylated polyether wax formulas x has a value ofgreater than 0, preferably 1 to 70; y has a value of greater than 0,preferably 1 to 70; and z has a value of 1 to 400, preferably 1 to 100.

The polymeric structure of the siloxylated polyether waxes is notspecifically limited, however, the siloxylated polyether waxes should beselected such that the melting point is greater than 37° C. but lessthan 200° C. Preferably the siloxylated polyether waxes useful in theinstant invention should have a melting point of between 50° C. and 150°C. Siloxylated polyether waxes useful in the instant invention are knownin the art.

The siloxylated polyether wax (iii) is employed in an amount of 1 to 20weight percent, preferably from 5 to 15 weight percent, based on thetotal weight of the silicone resin (i) and the silicone fluid (ii).

The siloxylated polyether wax functions to decrease the dynamicviscosity of the hot-melt pressure sensitive adhesive at temperaturesequal to or less than 200° C. Desirable dynamic viscosities of thewax-containing adhesives at temperatures equal to or less than 200° C.are equal to or less than 800 poise.

In general small amounts of additional ingredients may be added to thecompositions of this invention. For example, antioxidants, pigments,stabilizers, fillers and others may be added as long as they do notmaterially alter the requirements of the desired composition. If thehot-melt silicone pressure sensitive adhesive compositions contain afiller it is desired that the filler be present in an amount of nogreater than 5 weight percent based on the total weight of the siliconeresin and silicone fluid.

Additionally, hot-melt PSA additives known in the art, which areeffective at reducing dynamic viscosity, such as the esters described inU.S. Pat. No. 4,865,920, herein incorporated by reference, thepolyphenylsiloxane fluids described in U.S. Pat. No. 5,162,410, hereinincorporated by reference, the non-flammable hydrocarbons described inEP Patent Application 0 443 759 and others, may be incorporated into thehot-melt silicone pressure sensitive adhesive compositions of theinstant invention.

The hot-melt silicone pressure sensitive adhesive compositions of theinstant invention are prepared by merely mixing the silicone pressuresensitive adhesive comprised of siloxanes (i) and (ii) with the selectedsiloxylated polyether wax. The hot-melt silicone pressure sensitiveadhesive is then heated to a coatable viscosity and coated on asubstrate. Optionally the coated compositions may be cured. When thecomposition is to be cured, the composition may further contain a curingcatalyst. It is preferred that such catalysts remain inactive at roomtemperature and temperatures reached during the hot-melt coatingprocess. Therefore, such catalysts that either become active attemperatures higher than that of the hot-melt temperatures or becomeactive upon exposure to another energy source such as UV light orelectron beam radiation, are most suitable. The amount of catalystemployed should be sufficient to accelerate the cure of the composition.This amount can be readily determined by one skilled in the art throughroutine experimentation and is typically about 0.1 to 1.0 percent basedon the weight of the total composition.

When using the hot-melt silicone pressure sensitive adhesivecompositions of the instant invention to coat a substrate, the methodcomprises the steps of (a) heating the hot-melt silicone pressuresensitive adhesive composition to a coatable temperature above 25° C.,(b) coating the heated hot-melt silicone pressure sensitive adhesivecomposition onto the substrate, and (c) cooling the coated hot-meltsilicone pressure sensitive adhesive until it is in a generallynon-flowing state. Typically, heating the hot-melt silicone pressuresensitive adhesive compositions of the instant invention to temperaturesabove 100° C., preferably 150° C., results in viscosities sutiable forcoating. These coatable temperatures are low enough so thatdecomposition of the composition does not occur. Lower temperatures mayresult in coatable viscosities depending on the coating equipment used,the desired end product, and the composition of the hot-melt siliconepressure sensitive adhesive composition. For example, the thicker thelayer of pressure sensitive adhesive desired, the higher the coatingviscosity can be.

When the hot-melt silicone pressure sensitive adhesive compositions ofthe instant invention are applied to a backing or substrate, thisprocedure may be accomplished by using any conventional means, such asroller coating, dip coating, extrusion, knife coating, or spray coating.

The hot-melt silicone pressure sensitive adhesive compositions of theinstant invention will adhere to many substrates, such as paper, cloth,glass cloth, silicone rubber, polyethylene, polyethylene terephthalate,polytetrafluoroethylene, glass, wood, metals, and skin. Therefore, thereare many uses for the hot-melt silicone pressure sensitive adhesivecompositions of the instant invention. Depending on the desired use, itmay be desirable to apply adhesion promoters on the substrate surfaceupon which the hot-melt silicone pressure sensitive adhesivecompositions will be placed.

The hot-melt silicone pressure sensitive adhesive compositions of theinstant invention are especially suitable for assisting in delivering abioactive agent, such as a drug to a bioactive agent-acceptingsubstrate, such as a patient's skin. The hot-melt silicone pressuresensitive adhesive compositions of the instant invention may be employedin several types of bioactive agent delivery modes. One mode is byincorporating the bioactive agent into the hot-melt silicone pressuresensitive adhesive composition on an impermeable backing which isthereafter attached to the bioactive agent-accepting substrate tocommence delivery. A second mode of delivery is achieved by attaching apermeable membrane of material to the bioactive-agent acceptingsubstrate using the hot-melt silicone pressure sensitive adhesivecomposition of the instant invention, and then, contacting a reservoirof a bioactive agent to the attached permeable membrane. The bioactiveagent may then pass from the reservoir through the permeable membraneand to the substrate for absorption. For this mode, a bioactive agentdelivery device may be made which includes (a) a container, (b) abioactive agent contained in the container and (c) the hot-melt siliconepressure sensitive adhesive composition of the instant invention on thecontainer for providing a means for adhering the container to thebioactive agent-accepting substrate. Another mode of delivery compriseseither the first or second mode however, the adhesive is placed on theimpermeable backing or the permeable membrane along the outsideperimeter of either the backing or membrane.

Due to the presence of the siloxylated polyether waxes in the hot-meltsilicone pressure sensitive adhesive composition of the instantinvention, the resulting adhesives have improved hydrophiliccharacteristics, thus allowing quicker delivery of drugs that arehydrophilic in nature. Further, the use of siloxylated polyether waxesreduces the dynamic viscosity of the PSA which improves the coatabilityof hot-melt silicone pressure sensitive adhesives at temperatures at orbelow 200° C.

So that those skilled in the art can understand and appreciate theinvention taught herein, the following examples are presented, it beingunderstood that these examples should not be used to limit the scope ofthis invention which is found in the claims attached hereto.

For the following examples:

RESIN A is a xylene solution of a resinous copolymeric siloxane preparedfrom 45 parts of sodium silicate and 20 parts (CH₃)₃ SiCl according tothe method of U.S. Pat. No. 2,676,182 to Daudt et al., which is herebyincorporated by reference. Resin A and contains Me₃ SiO_(1/2) units andSiO_(4/2) units in a ratio of approximately 0.75:1.0, has a nonvolatilecontent (NVC) of typically 69 to 71%, an acid number in the range of 0.3to 1.4, a viscosity in the range of 90 cSt at 25° C., and asilicon-bonded hydroxyl content of about 2.5 weight percent at 100% NVC.

FLUID A is a hydroxyl-endblocked polydimethylsiloxane fluid having aviscosity of about 13,500 cP at 25--C.

PSA 1 was prepared by mixing 27.2 parts Fluid A, 47.5 parts Resin A and11.6 parts xylene. The mixture was heated to 115° C. and anhydrousammonia was passed through the mixture to promote silanol condensation.Water produced from the condensation was continuously driven off untilthe desired viscosity was attained. The ammonia was then discontinued.13.6 parts of hexamethyldisilazane was then added to cap the residualsilanol and render the product non-reactive. The resulting product wasstripped and devolatized to 99% NVC to form the PSA.

PSA 2 was prepared by mixing 15.7 parts Fluid A, 31.1 parts Resin A and6.7 parts xylene. The mixture was heated to 115° C. and anhydrousammonia was passed through the mixture to promote silanol condensation.Water produced from the condensation was continuously driven off untilthe desired viscosity was attained. The ammonia was then discontinued.Nine (9.0) parts of hexamethyldisilazane was then added to cap theresidual silanol and render the product non-reactive. The resultingproduct was stripped to remove volatiles. 15 weight parts of 1,000 cStpolydimethylsiloxane fluid was then added to produce the PSA.

PSA 3 was prepared by mixing 31.5 parts Fluid A, 55 parts Resin A and13.5 parts xylene. The mixture was heated to 115° C. and anhydrousammonia was passed through the mixture to promote silanol condensation.Water produced from the condensation was continuously driven off untilthe desired viscosity was attained. The ammonia was then discontinued. 7weight parts of 100 cSt polydimethylsiloxane fluid was then added. Theresulting product was stripped to remove volatiles to 99% NVC.

WAX 1 is a siloxylated polyether wax having the formula ##STR2## whereA¹ is --(CH₂)₃ O(CH₂ CH₂ O)₃₂ COCH₃. Wax 1 has a melting point of 45° C.

WAX 2 is a siloxylated polyether wax having the formula ##STR3## whereA¹ is --(CH₂)₃ O(CH₂ CH₂ O)₃₂ COCH₃. Wax 2 has a melting point of 37° C.

WAX 3 is a siloxylated polyether wax having the formula ##STR4## whereA² is --(CH₂)₃₀ (CH₂ CH₂ O)₂₄ COCH₃. Wax 3 has a melting point of 36° C.

WAX 4 is a siloxylated polyether wax having the formula ##STR5## whereA¹ is --(CH₂)₃ O(CH₂ CH₂ O)32COCH₃. Wax 4 has a melting point of 43° C.

WAX 5 is a siloxylated polyether wax having the formula ##STR6## whereA³ is --(CH₂)₃ O(CH₂ CH₂ O)100COCH₃. Wax 5 has a melting point of 55° C.

The physical properties of release, adhesion and shear were measured onthe hot-melt silicone pressure sensitive adhesives Measurements wereobtained by testing a one inch wide polyester tape having a siliconepressure sensitive adhesive thereon. The hot-melt silicone pressuresensitive adhesives of the instant invention were cast to yield a 2 milthickness dry adhesive on "SCOTCH-PAK" 1022 Release liner, a polyesterfilm coated with a release coating available from 3M Company, St. Paul,Minn. After coating, a "MYLAR" polyester film was adhered to each castedsample with a 4.5 lb. rubber transfer roller.

The laminate was then cut into one-inch wide strips with the use of aone-inch tape specimen cutter received from the Pressure Sensitive TapeCounsel. The following properties were then measured:

RELEASE: The release values were obtained by stripping the tape from theSCOTCH-PAK 1022 Release Liner at a rate of 40 inches/minute at an angleof 180° while attached to a tensile testing machine. An average valueover the entire Length of the liner was recorded. Release values of lessthan 50 gm/cm are considered acceptable.

ADHESION: The adhesion values were obtained as follows. The tapes havingthe silicone PSA composition thereon were adhered to a stainless steelpanel with a 4.5 lb. roller and allowed to rest for 20 minutes. Theadhesion measurements were obtained by stripping each tape from thepanel at a rate of 12 inches/minute at an angle of 180° while attachedto a tensile testing machine. Desirable values range between about 100and about 2000 gm/cm.

SHEAR: Shear values were measured by cutting three strips of theprepared laminates 2.5 cm wide and 7.5 cm in length. A 3.5 cm wide by5.0 cm long strip of MYLAR is applied to the adhesive strip so as toprovide an overlap of 2.5 cm in lengthwise direction. These arelaminated using a 4.5 lb. roller and allowed to equilibrate for 20minutes. The specimen is mounted in the jaws of an Instron Model 1122Tensometer, available from Instron Corporation, and pulled at a speed of0.5 cm/min. and the peak load required to shear and separate thelaminate is recorded in Kg/6.25 cm². Desirable values range between 4and 25 kg/6.25 cm².

WATER SWELL: 5 to 7 gram samples of the adhesive were hot pressedbetween release liner to yield a dry adhesive film of 0.130 inchthickness at 125° C. Once cooled, the samples were weighed and placed ina petri dish lined with release liner. The samples were then coveredwith distilled water for 24 hours. The samples were removed andair-blown dried to remove surface water. The samples were then weighedagain to determine the water weight gain. The samples were then returnedto the water and the procedure repeated at 48 hours. A positive waterweight gain is desired.

DYNAMIC VISCOSITY (n*), ELASTIC STORAGE MODULI (G') and FLUID LOSSMODULI (G"): The dynamic viscosity, elastic storage moduli and fluidloss moduli were measured on the adhesive compositions using aRheometrics Dynamic Spectrometer, Model RDS2, available fromRheometrics, Piscataway N.J., and running a temperature sweep on 4 gramsamples of 1 mm thickness and operating the tester at a frequency of 100radians/sec. at a 1% strain using a 50 mm cup and plate. Desirabledynamic viscosities (n*) should be less than or equal to 800 poise at orbelow 200° C.

ELASTIC STORAGE MODULI (G'): Elastic storage modulus is related to dieswell and elastic memory. The higher the die swell, the smaller the sizeof an orifice required for a given coating thickness. Therefore, thelower the elastic storage modulus, the better, as it is then easier tocoat onto a substrate. Tests similar to those run in these examples aredescribed in ASTM 4065-82. Desirable storage modulus values should beless than 45,000 dynes/cm² at or below 200° C.

EXAMPLES 1-10

In Examples 1-5, 7 and 9 the hot-melt silicone pressure sensitiveadhesives compositions were prepared by mixing the compositionsindicated in Table 1 at 100° C. until homogeneously mixed and thenallowing the mixture to cool to room temperature. Examples 6, 8, and 10are provided to show the properties of the various silicone pressuresensitive adhesives without the siloxylated polyether waxes.

                  TABLE 1                                                         ______________________________________                                                  PSA Type    Wax       Weight %                                      Example # Employed    Employed  Wax*                                          ______________________________________                                        1         1           1         10%                                           2         1           2         10%                                           3         1           3         10%                                           4         1           4         10%                                           5         1           5         10%                                           6         1           none       0%                                           7         2           5         10%                                           8         2           none       0%                                           9         3           5         10%                                           10        3           none       0%                                           ______________________________________                                         *Based on the total weight of the silicone fluid and silicone resin in th     PSA composition.                                                         

As shown in Table 2, these adhesives were evaluated for physicalproperties of release (g/cm), adhesion (g/cm), shear (Kg/6.25cm²) andwater swell (%, 24 and 48 hr.). Release values ranged between 4 and 24g/cm and all samples were within the acceptable range of less than orequal to 50 gm/cm. Adhesion values ranged between 0 and 350 g/cm andsamples 4, 5, 7 and 9 were within the acceptable range of 100-2,000gm/cm. Shear values ranged from 0 to 11.6 Kg/2.5cm² and samples 5 and 7were within the acceptable range of 5 to 25 kg/6.25 cm². All of thesamples showed a positive water swell which indicates that the PSA's arehydrophilic in nature. These results show that the addition ofsiloxylated polyether waxes to the PSA's does not adversely affect thephysical properties of the PSA's.

                  TABLE 2                                                         ______________________________________                                                                           Water Swell                                        Release   Adhesion Shear   %                                          Example #                                                                             g/cm      g/cm     Kg      24 hrs                                                                             48 hrs                                ______________________________________                                        1       14         23      0.7     2.4  2.8                                   2       10         0       0.0     1.4  2.0                                   3       25         3       0.7     1.6  2.3                                   4        4        299      4.1     1.4  2.4                                   5        7        347      11.6    1.9  2.7                                   6        4        597      13.5    --   0.4                                   7        6        184      5.0     1.2  1.9                                   8       16        206      8.0     0.03 0.15                                  9        5        331      3.0     3.3  4.4                                   10      13        310      4.5     0.04 0.2                                   ______________________________________                                    

Results of dynamic viscosity, elastic storage moduli and fluid lossmoduli are given in Table 3. Decreased dynamic viscosity values aredesirable to improve coatability without solvents. Each samplecontaining the siloxylated polyether wax demonstrated the desirabledecreasing dynamic viscosity in comparison to the control PSA.

                  TABLE 3                                                         ______________________________________                                        Example                                                                              50° C.     200° C.                                       #      G'      G"        N*    G'    G"    N*                                 ______________________________________                                        1      640,000 180,000   6,600 33,000                                                                              44,000                                                                              550                                2      640,000 190,000   6,600 37,000                                                                              49,000                                                                              620                                3      630,000 190,000   6,600 31,000                                                                              42,000                                                                              510                                4      670,000 180,000   6,900 20,000                                                                              28,000                                                                              350                                5      560,000 210,000   5,900 25,000                                                                              35,000                                                                              460                                6      702,500 148,800   7,180 84,500                                                                              92,400                                                                              1250                               7      480,000 1,000,000 12,000                                                                               7,800                                                                              17,000                                                                              190                                8      550,000 1,500,000 16,000                                                                              12,000                                                                              29,000                                                                              310                                9      *       *         *     *     *     *                                  10     340,000 490,000   66,000                                                                               6,000                                                                              18,000                                                                              190                                ______________________________________                                         *Unable to compress material between plates to 1 mm gap, no test run.    

What is claimed is:
 1. A method of coating a hot-melt silicone pressuresensitive adhesive composition onto a substrate, comprising:(a)preparing a hot-melt silicone pressure sensitive adhesive by mixingtogether (I) a silicone pressure sensitive adhesive selected from thegroup consisting ofa mixture of (i) a hydroxyl-functionalorganopolysiloxane resin comprising R₃ SiO_(1/2) siloxane units andSiO_(4/2), wherein R is selected from a monovalent radical selected fromthe group consisting of hydrocarbon and halogenated hydrocarbon radicalshaving 1 to 20 carbon atoms and (ii) a hydroxyl-terminateddiorganopolysiloxane polymer containing repeat units of R₂ SiO_(2/2)siloxy units wherein R is independently selected from a monovalentradical selected from the group consisting of hydrocarbon andhalogenated hydrocarbon radicals having 1 to 20 carbon atoms; and acondensed product of (i) and (ii); and (II) from about 1 to 20 weightpercent, based on the total weight of (I) of a siloxylated polyether wax(b) heating the hot-melt silicone pressure sensitive adhesive to acoatable temperature of between about 85° C. and 200° C.; (c) coatingthe hot-melt silicone pressure sensitive adhesive onto a substrate; and(d) cooling the hot-melt silicone pressure sensitive adhesive until itis in a non-flowing state.
 2. The method of coating as claimed in claim1 wherein the hot-melt silicone pressure sensitive adhesive is heated toa coatable temperature of between 150° C. to 200° C.
 3. The method ofcoating as claimed in claim 1 wherein the substrate is selected from thegroup consisting of paper, cloth, glass cloth, silicone rubber,polyethylene, polyethylene terephthalate, polytetrafluoroethylene,glass, wood, metals, and skin.